Support sprintf-formatting for retention_policy

[Thor77]

I have a Logstash-configuration which gathers data from multiple inputs with different intervals but writes them to the same database.
In this case I would like to choose a lower retention time for the input with lower intervals to not need more storage.
As the retention_policy-argument doesn't support sprintf-formatting, though, I don't see a way to realise this without splitting my config (which I would like to avoid).
Am I missing anything? Is there a better/any way to accomplish this at the moment?